Tetrachloro-ortho-Benzoquinone as Catalyst for Electrocatalytic Oxidation of Sulfite in Acidic Media and its Analytical Application

A chemically modified carbon paste electrode (mcpe) with tetrachloro-orthobenzoquinone(tob) was employed to study the electrocatalytic oxidation of sulfite inaqueous solution using cyclic voltammetry (cv) and double-potential stepchronoamperometry. it has been found that under an optimum condition (ph 2.0), theoxidation of sulfite at the surface of mcpe occurs at a potential of about 700 mv lesspositive than that of an unmodified cpe. the diffusion coefficient (d) for sulfite was foundas 8.2×10-6 cm2 s-1 by chronoamperometry. the electron transfer coefficient, a, was estimatedto be 0.4 and 0.24 for the oxidation of sulfite at the surface of mcpe and unmodified cpe,respectively. the electrocatalytic oxidation peak currents showed a linear dependence on thesulfite concentration in the range of 1×10-4 m -4.2×10-3 m with detection limit (3s) 5.7×10-5m by cv. this method was also used for selective determination of sulfite in weak liquor